Abstract:

Elucidating the mechanisms underlying the stability of microbial communities in soil is crucial to understandingtheir ecological advantages. Most studies were predominantly focused on microbial community diversity andcomposition, while the assembly processes and stabilization of microbial communities remain unclear. Here, weinvestigated stability of microbial communities and assembly processes in soil under intercropping. Three typicalintercropping systems (8-12 y): maize-wheat (MlW), maize-pea (MlP), and maize-green manure (MlG) wereestablished, to assess broad range of factors affecting microbial network assembly. Compared with monoculturemaize, intercropping reshaped the microbial community structure, preferentially enriching non-dominant phy-la-Cyanobacteria (nitrogen fixation, +166%) and Fibrobacterota (cellulose decomposition, +205%). This shiftfostered a community with greater fitness, manifested as a 34% increase in average niche breadth and a 16%increase in stability. Intercropping drove dual pathways to increase microbial community stability. Firstly,intercropping simplified microbial interactions, as evidenced by a 58% and 73% reduction in the complexity ofbacterial and fungal co-occurrence networks, respectively. Concurrently, network modularity increased by 23%and the number of keystone taxa doubled. Secondly, the community assembly was increasingly governed bystochasticity, evidenced by an 11% increase in neutral model fit. This shift was characterized by a 17% reductionin homogeneous selection for bacteria due to heterogeneous environment under intercropping. Additionally,modularity increased stochastic processes dominated by ecological drift by 16%. This finding suggests a contextdependent alternative to the "complexity reinforces stability" paradigm, revealing that simplified networks andstochastic ecological drift enable intercropping systems to effectively withstand environmental disturbances.